Sparkplug Confusion and Tohatsu Carb Question?

[Troutboy NZ]

Gidday from New Zealand! I have a 2005, M40D2 Tohatsu 40hp (under the guise of a Mercury Lightning XR). I am confused as to which sparkplug to run in it. The factory manual that came with the engine says run a BR7HS-10, but the sticker under the engine cowling on the block says to run the BR8HS-10... a colder plug, and as I understand the plug that is recommended for the 50hp Tohatsu, not the 40hp?

Now I know both these engines are the same basically, which should I be running?

Also the mixture screw settings are confusing me. The motor has done approx 50 hours now and the screws were all about 3.5 - 4 turns from seated, this seems too much to me and would explain the slightly oily plugs - it was however still running fine. Can anyone please give me the starting point for the mixture screw settings on this 40hp and what you find is optimum?

Thanks

 

[TOHATSU GURU]

Re: Sparkplug Confusion and Tohatsu Carb Question?

B7HS-10 or the BR7HS-10.

2.5 intial w +-3/4

2 3/4 is where we start and it usually isn't more than a 1/4 turn either way per carb.

 

[Troutboy NZ]

Re: Sparkplug Confusion and Tohatsu Carb Question?

Thanks very much - just the starting point I wanted to hear. As a side I tried a new set of BR8HS-10 alongside another new set of BR7HS-10 and the 8's performed better in my mind, although I had to nudge the idle up a fraction to compensate for the cooler plug.

Andrew